CP Violation in B Decays Vivek Sharma University of California at San Diego this is a test where do these notes get displayed? Vulcano Workshop 2006

From Cosmos To Quarks ! The universe is now matter dominated: where has all the primordial anti-matter gone? Anti-proton/proton ratio ~10-4 in cosmic rays; no evidence for annihilation photons from intergalactic clouds Sakharov conditions (1967) for generation of cosmological asymmetry: Baryon number violation, e.g., proton decay Thermal non-equilibrium Violation of C, CP discrete symmetries CP Violation seen in Particle decays What, if any, is the connection between CP violation in the cosmos and the CPV in subatomic systems ?

CP Violation In Subatomic Systems CP Violation first discovered in the Kaon system Kaon system has been the playground of CPV model-building (and model-killing ) since discovery (1964) Kobayashi & Maskawa’s proposition (1973) of CPV in the context of the complex weak couplings of 3 generations of quarks consistent with observed CPV in the Kaon system (postdiction!) But hadronic uncertainties in the Kaon system makes clean interpretation of CPV in terms of SM or New Physics difficult B mesons are the “new” & theoretically clean laboratory for investigation of CP Violation within SM & Beyond Standard Model Two dedicated experimental efforts: PEP-II Collider & BaBar detector in California KEK-B Collider & Belle detector in Japan

Asymmetric Energy e+ e- Colliders: B Factories BaBar@ PEP-II Belle @ KEK-b 350 fb-1 500 fb-1

Belle and Babar Detectors  Enough energy to barely produce 2 B mesons, nothing else! B mesons are entangled  Need for Asymm energy collisions

CP Violation Studies at Asymmetric Energy Colliders

Inter Quark Couplings: CKM Matrix W- gVcb W- gVub Flavor changes through mixed couplings to quarks Cabibbo-Kobayashi-Maskawa (CKM) Matrix Unitary matrix described for 3 generations of quarks by 3 rotation angles and 1 non-trivial phase KM Conjecture: The phase of CKM matrix is source of CPV

CKM Matrix: Phenomenology ckm phase 1 l Wolfenstein parameterization: Observed experimental hierarchy l ~ 0.22 sinθC Cabibbo angle l 1 2x2 submatrix: u,d,s,c quarks only 3x3 matrix: 3 quark generations 3 ® 1 ~l3 2 ® 1 ~l CKM Phase: changes sign under CP 1 3 ® 2 ~l2

The Unitarity Triangle For B System Angles of Unitarity Triangle Specific forms of CP Violation in B decay provide clean information about the angles of the UT triangle Same triangle also defined by length of its sides (from CP conserving B decay processes such as b u l nu )  Overconstrained triangle

CP Violation As Quantum Interference Analogous to a two-slit quantum interference experiment! CPV due to interference of meson decay amplitudes G(B ® f ) G(B ® f )

Direct CP Violation in B0 K Classic example of Quantum Interference Loop diagrams from New Physics (e.g. SUSY) can modify SM asymmetry contributing to the Penguin (P) amplitude Measurement is a simple “Counting Experiment”

Direct CP Violation in B0K+p- Bkgd symmetric! 4.2, syst. included BaBar LARGE CP Violation ! unlike Kaon system

B0 Mesons Oscillate, Lead To CP Violation Oscillation via spontaneous 2nd order weak transition Sensitive to new particle of BSM (H+ etc) ARGUS Involves Vtd = | Vtd |eib Event with 2 B0 (instead of B0 B0)

CPV Due To Interference of B Mixing & Decay CPV through interference between mixing and decay amplitudes Time-dependent asymmetry

Case Of Single Decay Amplitude CPV through interference between mixing and decay amplitudes Directly related to CKM angles for single decay amplitude Time-dependent asymmetry For the simple case shown with single decay mechanism

SM Predicts Large CPV in B K0 Golden Channel CP Eigenstate: hCP = -1: Ks hCP = -1: KL Amplitude of CP asymmetry Quark subprocess B0 mixing K0 mixing ~0.7 instead of 2x10-3 in Kaons!

Steps in Time-Dependent CPV Measurement z distinguish B0 Vs B0 m- K- bgU(4S) = 0.55 Coherent BB pair B0 B0  J/y Ks Vivek Sharma , UCSD

Effect of Mis-measurements On Dt Distribution perfect flavor tagging & time resolution realistic mis-tagging & finite time resolution CP PDF

B Charmonium Data Samples 4370 events 572 events MES [GeV] MES [GeV] CP sample NTAG purity ηCP J/ψ KS (KS→π+π-) 2751 96% -1 J/ψ KS (KS→π0π0) 653 88% ψ(2S) KS (KS→π+π-) 485 87% χc1 KS (KS→π+π-) 194 85% ηc KS (KS→π+π-) 287 74% Total for ηCP=-1 4370 92% J/ψ K*0(K*0→ KSπ0) 572 77% +0.51 J/ψ KL 2788 56% +1 Total 7730 78% BABAR 2788 events (ηCP = +1) ΔE [MeV]

Sin(2b) Result From B Charmonium K0 Modes (2004) (cc) KS modes (CP = -1) J/ψ KL mode (CP = +1) background hep-ex/0408127 sin2β = 0.722  0.040 (stat)  0.023 (syst) (PRL 89, 201802 (2002): sin(2β) = 0.741 ± 0.067 ± 0.034)

Angle  From B0 +- Neglecting Penguin diagram (P) T P

Angle  From B0 +- World Average:

Direct CPV In BDK Decay  Angle  Constraint on g in the r,h plane measurements data limited (~ 2.4)

The Unitarity Triangle Defined By CPV Measurements Precise Portrait of UT Triangle from CPV Measurements

UT With CPV & CP Conserving Measurements Incredible consistency between measurements ! Paradigm shift ! SM/CKM Picture Describes observed CPV Look for NP as correction to the CKM picture

Searching For New Physics by Comparing Pattern of CP Violation in Penguin Decays of B Mesons

Comparing CP Asymmetries : Penguins Vs Tree In SM both decays dominated by a single amplitude with no additional weak phase Tree New physics coupling to Penguin decays can add additional amplitudes with different CPV phases Penguin 3 New Physics

New Physics ? Standard Model

Naïve Ranking Of Penguin Modes by SM “pollution” Naive (dimensional) uncertainties on sin2 Decay amplitude of interest SM Pollution f f SuperGold Gold Bronze Note that within QCD Factorization these uncertainties turn out to be much smaller !

Golden Penguin Mode : B0   K0 BaBar: 222M BB hep-ex/0502019 Modes with KS and KL are both reconstructed (Opposite CP) full background continuum bkg 114 ± 12 signal events 98 ± 18 signal events

CP analysis of ‘golden penguin mode’ B0   K0 BaBar (Opposite CP) S(fKS) = +0.29 ± 0.31(stat) S(fKL) = -1.05 ± 0.51(stat) Standard Model Prediction S(fK0) = sin2b = 0.69 ± 0.03 C(fK0) = 1-|l| = 0 Combined fit result 0.8s hfK0

Golden penguin mode: B0  h’K0 hep-ex/0502017,0507087 B0  h’KS B0  h’K0 Large statistics mode Reconstruct many modes ’   + –, 0      ,  + –0 KS  + – ,00 BaBar hfK0  sin2 [cc] @ 2.7 ’KS 819 ± 38 signal events (Ks mode) 440 ± 54 signal events (KL mode)

Bottom line Taken individually, each decay mode in reasonable agreement with SM but (almost) all measurements are lower than sin2 from ccs Naïve b  s penguin average sin2eff = 0.50 0.06 Compared to Tree: sin2eff = 0.69 0.03 Theory models predict SM pollution to increase sin2eff !!

Theory Predictions, Accounting For subdominant SM Amplitudes 2-body: Beneke, PLB 620 (2005) 143 Calculations within framework of QCD factorization 3-body: Cheng, Chua & Soni, hep-ph/0506268 sin2eff > 0.69  larger discrepency !

What Are s-Penguins Telling Us ? This could be one of the greatest discoveries of the century, depending, of course, on how far down it goes… 2.4s? discrepancy

Need More Data To Understand The Puzzle Luminosity expectations: K*g 2004=240 fb-1 2008=1.0 ab-1 f0KS KSp0 jKS h’KS KKKS 4s discovery region if non-SM physics is 0.19 effect 2004 2008 Individual modes reach 4-5 sigma level Projections are statistical errors only; but systematic errors at few percent level

Projected Data Sample Growth 20 Double again from 2006 to 2008 ICHEP08 Integrated Luminosity [fb-1] PEP-II: IR-2 vacuum, 2xrf stations, BPM work, feedback systems BABAR: LST installation 4-month down for LCLS, PEP-II & BABAR 17 Double from 2004 to 2006 ICHEP06 12 Lpeak = 9x1033 Expect each experiment to accumulate 1000 fb-1 by 2008

Summary & Prospects CP Violation in B decays systematically studied at BaBar & Belle. A Comprehensive profile emerging Standard Model picture (3 generation CKM matrix) of CP Violation consistent will all observations SM CPV too weak to explain cosmic CPV New Physics (in loops) can still contribute to observed CPV but is unlikely to be the dominant source CPV violation in the (rare) Penguin Decays appears lower than SM predictions (> 2.4) more data needed to reveal true nature of discrepancy B-factories expect to triple data sets by 2008 Super B-factories after then…

Backup Slides

B Meson: Special Laboratory for CPV Investigations Large Mass : MB=5.279 GeV/c2 “Large” lifetime: Large mixing Large rate for penguin decays Exclusive B decays Long B lifetime B0 B0 oscillations Observation of BK* g

Direct CPV in s-Penguins ? No sign of direct CPV !

Must be if one amplitude dominates Compare sin2 with “sin2” from CPV in Penguin decays of B0 Both decays dominated by single weak phase Tree: Penguin: New Physics? 3 ? Must be if one amplitude dominates

Must be if one amplitude dominates Compare sin2 with “sin2” from CPV in Penguin decays of B0 Both decays dominated by single weak phase Tree: Penguin: New Physics? 3 ? Must be if one amplitude dominates

Direct CP Violation in B0 K : Belle (386M BB) Combined significance >> 6 Belle Rules out Superweak model Establishes CPV not just due to phase of B Mixing But hadronic uncertainties preclude determination of CKM angle   challenge to theory

An Optimist’s Global CKM fit ? : 2008 (1 fb-1 each) 95% contours ?

CP Violation CP violation can be observed by comparing decay rates of particles and antiparticles The difference in decay rates arises from a different interference term for the matter vs. antimatter process. Analogy to double-slit experiment: source Classical double-slit experiment: Relative phase variation due to different path lengths: interference pattern in space

CP Violation Is a Quantum Phenomenon CPV is due to Quantum interference between > two amplitudes Phases of QM amplitudes is the key Need to consider two types of phases CP-conserving phases: don’t change sign under CP (Sometimes called strong phases since they can arise from strong, final-state interactions) CP-violating phases: these do change sign under CP transformation (originate in the Weak interaction sector)

Definition of CP Asymmetry To extract the CP-violating phase from an observed CP asymmetry, we need to know the value of the CP-conserving phase difference B system: extraordinary laboratory for quantum interference experiments: many final states, multiple “paths” Lots of channels for CP Violation

The CKM matrix & its mysterious pattern (Wolfenstein parametrization) The SM offers no explanation for this numerical pattern. But SM framework is highly predictive: Unitarity triangle: (Col 1)(Col 3)* =0 etc. Only 4 independent parameters: A, l, r, h One independent CP-violating phase parameter

Impressionist’s View of The CKM matrix Largest phases in the Wolfenstein parametrization Magnitudes of CKM elements u d t c b s l3 1 l 1 l2 l 1 1 l3 l2 Note: all terms in the inner product between columns 1 and 3 are of order l3. This produces a unitarity triangle of roughly equal sides.

Machine Performance Exceeds Design (x3) Peak luminosity (cm-2 s-1) 1.0025 x 1034 Best shift 247.2 pb-1 Best day 710.5 pb-1 Best week 4.464 fb-1 Best month 17.036 fb-1 BABAR logged 343 fb-1 96% efficiency over the entire history of BABAR BABAR, Run 5 KEK-B operation even more spectacular !

CP violation in the B system CPV through interference between mixing and decay amplitudes Directly related to CKM angles for single decay amplitude Time-dependent asymmetry

CP violation in the B system CPV through interference between mixing and decay amplitudes Directly related to CKM angles for single decay amplitude Time-dependent asymmetry For simple case shown with single decay mechanism

The Unitarity Triangle Defined By CPV Measurements New B Factory milestone: Comparable UT precision from CPV in B decays alone

A fundamental cosmological question The universe is now matter dominated: where has all the anti-matter gone? Anti-proton/proton ratio ~10-4 in cosmic rays; no evidence for annihilation photons from intergalactic clouds Cosmological generation of asymmetry: Sakharov conditions (1967) Baryon number violation, e.g., proton decay Thermal non-equilibrium Violation of CP discrete symmetry Broken Phase: Massive quarks, W, Z bosons Unbroken Phase: Massless quarks Transition to broken electroweak symmetry provides these conditions Connection between CPV in cosmos & subatomic particles ?

Direct CP Violation in B0 K : BaBar 4.2 effect (syst. included) similar results from Belle

CP Violation & Sensitivity To New Physics New physics at the electroweak scale generically introduces many new large flavor-violating or CP-violating couplings to quarks Quantum loop diagrams can attract couplings to heavy new particles of BSM physics Theory robust : capable of discriminating between SM and New Physics in special cases